Growers should be watching temperatures closely tonight into Tuesday morning. Check NEWA for the nearest weather station to your farm.
Estimated temperatures tonight across the state:
• Pittsfield / Berkshires: 22°F
• Amherst / Pioneer Valley: 27°F
• Worcester / central MA: 29°F
• Taunton / southeastern MA: 29°F
• Boston area: 32°F
• Plymouth / coastal southeast MA: 34°F
These are reference points. Growers should check their closest NEWA station and, ideally, a field thermometer placed at canopy or flower height in the coldest part of the field for accuracy.
How long does it need to be cold?
Most critical temperature charts are based on about 30 minutes of exposure at that temperature. That does not mean damage only happens at exactly 30 minutes, but it gives us a useful reference point. A short dip may cause less injury than several hours below the critical temperature. Cold pockets, strong wind, clear skies, and low field areas can make the situation worse.
Strawberries:
For strawberries, the most sensitive tissue right now is the flower. Start paying close attention when the forecast is 32°F or lower, especially if there are exposed buds or open blossoms. A weather station reading of 32°F can still mean colder temperatures at blossom height in a low part of the field.
Strawberry stage Approx. critical temp
Tight bud 25°F
Popcorn stage 26°F
Open blossom 30°F
Fruit 28°F
When to take action:
If open blossoms are present and the field-level forecast is near 30°F or lower, row cover should be strongly considered. If the field is at popcorn stage or tight bud and temperatures are forecast in the mid-20s, protection is also warranted. This is especially important where the cold is expected to last more than 30 minutes.
Blueberries:
For blueberries, the answer depends heavily on bud stage. If blueberries are still mostly at bud swell or very early stages, the risk is lower. The concern increases quickly once flowers are visible, separated, pink, open, or at petal fall.
Blueberry stage Approx. tolerance / injury concern
Bud swell 10–15°F
Tight cluster 20–23°F
Early pink bud 23–25°F
Late pink bud 24–27°F
Full bloom 28°F
Petal fall / small green fruit 32°F (injury possible)
When to take action:
For advanced blueberry blocks, especially early varieties and warm sites, start paying close attention when the forecast is in the low 30s. If plants are at full bloom, take the event seriously when temperatures approach 28°F. If plants are at petal fall or small green fruit, even temperatures near 32°F can be a problem. That stage is no bueno for cold tolerance.
Practical steps for this event
For strawberries, cover fields with exposed buds or open blossoms where possible. Put row cover on before dark so it can trap some field heat and seal the edges well. For blueberries, prioritize early varieties, advanced bud stages, and cold pockets. Bud stage matters more than the crop name alone. If using overhead irrigation for frost protection, only use it if the system is designed for frost protection and can run continuously until ice begins melting after sunrise. Starting and stopping at the wrong time can make injury worse. If using plastics, avoid laying directly over plants. Also avoid pushing new tender growth with fertilizer right before a cold event.
John G’s final thoughts:
This is not a panic situation, but it is a night to be prepared. The highest concern is for open strawberry blossoms, advanced blueberry buds, early varieties, and low fields where cold air settles. Check NEWA, check your field thermometer, and make decisions based on the crop stage in each block.
Extra Resources:
https://www.canr.msu.edu/blueberries/weather/critical-spring-temperatures
